Block copolymer compositions

ABSTRACT

ADHESIVES, INKS, PRIMERS, ETC., IN WHICH TACKIFYING RESINS ARE COMBINED WITH CERTAIN POLY ALPHA-OLEFIN BLOCK POLYMERS, HAVE EXCELLENT SPECIFIC ADHESION TO LOW ENERGY SURFACES SUCH AS POLUTHYLENE AND POLYPROPYLENE AS WELL AS TO SUCH OTHER SURFACES AS METAL, WOOD, PLASTICS, GLASS AND RUBBER. THE POLYMER IS A BLOCK ALPHA-OLEFIN WHICH HAS THE GENERAL FORMULA A-(B-A)N WHEREIN A BLOCKS ARE AT LEAST CAPABLE OF CRYSTALLIZATION AND B BLOCKS ARE SUB STANTIALLY AMORPHOUS.

United States Patent 3,649,579 BLOCK COPOLYMER COMPOSITIONS RamsisGobran, Roseville, Leon V. Kremer, Cottage Grove, and Dolores 0. Ethier,White Bear Lake, Minn, assignors to Minnesota Mining and ManufacturingCompany, St. Paul, Minn.

N0 Drawing. Continuation-impart of application Ser. No. 707,976, Feb.26, 1968. This application Jan. 27, 1969, Ser. No. 794,354

Int. Cl. C09j 3/26 US. Cl. 260-27 Claims ABSTRACT OF THE DISCLOSUREAdhesives, inks, primers, etc., in which tackifying resins are combinedwith certain poly alpha-olefin block polymers, have excellent specificadhesion to low energy surfaces such as polyethylene and polypropyleneas well as to such other surfaces as metal, wood, plastics, glass andrubber. The polymer is a block alpha-olefin which has the generalformula A(BA) wherein A blocks are at least capable of crystallizationand B blocks are substantially amorphous.

FIELD OF THE INVENTION This application is a continuation-in-part ofSer. No. 707,976, filed Feb. 26, 1968, and now abandoned.

This invention relates to poly alpha-olefin block polymers and toimproved coating compositions and adhesive tapes made therefrom. Moreparticularly, it relates to tackified hydrocarbon solvent-dispersibleelastomeric substantially linear poly alpha-olefin block polymers,having improved adhesion to low energy surfaces together with excellentelongation, tack, cohesive strength, and heat resistance.

Low energy surfaces such as polyethylene and polypropylene have limiteduse because they are notoriously unreceptive to adhesives, inks,primers, etc. For example, there has long been a need for an adhesive toadhere molded polypropylene machine parts to each other, paper and foillabels to polyethylene and polypropylene bottles, and laminating film tofurniture. A truly satisfactory adhesive for such purposes shoulddesirably have, in addition to afiinity for both low and high energysurfaces, high tensile and cohesive strength without chemicalcrosslinking, dispersibility in hydrocarbon solvents, long shelflife andstability, insensitivity to oxidizing agents, high ultimate elongation,and resistance to softening up to at least 120 F.

A particularly acute commercial need for an adhesive having theforegoing characteristics is in the application of self-supportingprotective and decorative laminating films, especially polyethylene orpolypropylene. The strength, toughness, and resistance to cookingingredients make such films ideally suited for utilization as overlaysor veneers for furniture, countertops and the like, but heretofore noadequate adhesive has been found. Attempted laminations failed with thefilm pulling away from the metal, wood, or plastic substrate.

3,649,579 Patented Mar. 14, 1972 Hot melt adhesives, formed by combiningtackifiers with polyethylene, polypropylene, or copolymers thereof, aredisclosed in US. Pats. 2,894,925 and 3,220,966 and British Pats. 915,622and 1,019,851. A major problem with these adhesives is that they do notadhere unless bonded at elevated temperatures thereby precluding theiruse on heat-sensitive substrates or applications where it is noteconomically practical to utilize expensive hot melt equipment. They arealso insoluble in the solvents common to the adhesive art.

Many attempts have been made to prepare suitable adhesives, inks,primers, etc. for low energy surfaces that can be applied at roomtemperature conditions, by compounding low molecular weight solubleethylenepropylene random copolymers. Similarly, compounding attemptshave been made with styrene-butadiene rubbers. Where compatibletackifiers were found, the resultant compositions were gummy, weak, andlow in both adhesion and cohesive strength. Such compounding attemptshave yielded compositions which are unsatisfactory for mostapplications.

Block copolymers have been suggested as the main ingredient of generalpurpose adhesives having relatively high tensile strength and solubilityin hydrocarbon solvents. See, e.g., US. Pat. 3,239,478, which suggestsblock copolymers wherein the blocks are either polymers of a vinyl areneor a conjugated diene. Such copolymers, however, have easily oxidizeddouble bonds, making them especially susceptible to oxidation. They alsolose their rubber-like properties at temperatures above 5060 C. and lackadhesion to low energy surfaces. US. Pat. 3,378,606 disclosessemicrystalline stereoblock poly alphaolefins having plastic-rubberproperties and British Pat. 957,070 discloses crystallizable stereoblockpoly alphaolefin copolymers having rubber-like or elastomericproperties. However, these copolymers with few exceptions are notdispersible in nor suggested to be dispersible in hydrocarbon solventsat room temperature to provide smooth, pourable, stable, homogeneousdisper- SlOIlS.

SUMMARY OF THE INVENTION This invention provides compositions ofadhesives, inks, primers, etc., which have high tensile and cohesivestrength without chemical cross-linking, are readily dispersible inhydrocarbon solvents at room temperature, are elastomeric, have littlesensitivity to oxidizing agents, and do not soften at temperatures up toat least F. Pressuresensitive, solvent-dispersed, solvent-activated, andheatactivated adhesive as well as compositions such as printing inks andpaint primers can be prepared, permitting adhesion to a wide variety ofboth low and high energy surfaces, including polyethylene,polypropylene, nylon, polyester, polyformaldehyde, polyvinylidenechloride, polycarbonate, polystyrene, polyvinyl chloride, glass, steel,aluminum, wood, cloth, paper, ceramics, paint, rubber, etc. Adhesivesmade in accordance with the invention are thus suited for thepreparation of laminated structures having a polypropylene surface.Adherence is so tenacious that it is almost impossible manually to peelapart a laminated panel. Inks made in accordance with the invention areadmirably suited for printing on polyethylene or polypropylene films andarticles; similarly, primers made in accordance with the invention arewell suited for providing excellent adhesion of paints, etc., to bothhigh and low energy surfaces.

Pressure-sensitive adhesives prepared in accordance with the inventionare ideally suited for pressure-sensitive tapes having good adhesion tolow energy surfaces; in.

fact, it is usually unnecessary to prime the backing, particularly wherethe backing is a polyethylene or polypropylene film. Similarly, it ispossible to readily prepare pressure-sensitive or heat active transferfilms on release liners for use as unsupported adhesive tapes. Theseadhesives are also ideally suited for use in adhering selfsupportingprotective and decorative laminating films, particularly polyethylene orpolypropylene.

The adhesives, inks, primers, etc., comprise a substantially linear polyalpha-olefin block polymer having the general configuration A(B.-A) andan appropriate amount of tackifier. A designates a thermoplastic polyalpha-olefin block that is at least capable of crystallization, has aglass transition temperature ,above about 60 C. and a crystallinemelting point above 100 C. B designates a thermoplastic polyalpha-olefin block that is substantially amorphous, and has a glasstransition temperature below about C. The subscript n represents aninteger of at least 1. The overall polymer itself exhibits at least oneglass transition temperature below about 0 C., at least one above about60 C., a crystalline melting point above 50 C. and is characterized bycase of dispersibility in such hydrocarbon solvents as heptane, hexane,toluene, xylene and cyclohexane, or blends thereof to provide smooth,pourable, stable, homogeneous dispersions.

These substantially linear block polymers behave like other knowncrystallizable rubbers, e.g., natural rubber, and the knownnon-crystalline plastic-rubber block polymers, e.g.,styrene-butadiene-styrene copolymers, characteristically having a highultimate tensile strength so long as the blocks capable ofcrystallization are adequately large in relation to the total blockpolymer. This condition is satisfied when the substantially amorphousblocks constitute between about to 90 mole percent of the total blockpolymer and the blocks capable of crystallization constitutecorrespondingly between about 90 to 10 mole percent of the total blockpolymer. The polymers all have a minimum elongation of about 400 percentand a minimum ultimate tensile strength of about 200 pounds per squareinch. These block polymers exhibit the property of ease ofdispersibility in hydrocarbon solvents at room temperature to providesmooth, pourable, stable homogeneous dispersions if the substantiallyamorphous blocks are of the above mentioned size. Dispersibility isenhanced when the substantially amorphous blocks preferably constitutebetween about to 75 mole percent of the total block polymer and theblocks capable of crystallization constitute correspondingly betweenabout 75 to 25 mole percent of the total block polymer. Stabledispersions are those which do not irreversibly coagulate during longterm storage.

The overall properties of the polymer are dependent on the type andamount of catalyst used, the particular monomers used in the A and Bblocks, and the reaction temperature.

A and B blocks are connected in a regularly alternating sequence, withthe terminal positions occupied by A blocks. Although 5 or more blocksare satisfactory, the presently preferred polymers have 3 alternatingblocks, primarily because the polymer cost is directly proportional tothe number of blocks in the chain. The A blocks which are at leastcapable of crystallization are those which if annealed, by being heateduntil almost melted and then slowly cooled, will exhibit crystallinitywhich is detectable by thermal analysis such as differential thermalanalysis or differential scanning colorimetry.

Each A block is in essence a discrete polymer at least capable ofcrystallization and which is formed from one or more alpha-olefinmonomers selected from the group consisting of propylene and butene-l. Amonomer selected for an A block is such that it is capable of beinghomopolymerized to yield a polymer having a crystalline melting pointabove about 100 C. and a glass transition temperature above about 60 C.

Each B block is in essence a discrete substantially amorphous polymerformed from one or more alphaolefin monomers each of which has thegeneral formula C H wherein n is an integer from 2 to 12. A monomer ormixture of monomers selected for a B block must be such that it iscapable of being polymerized in a manner to yield substantiallyamorphous polymer having a glass transition temperature below about 0 C.Preferred alphaolefin monomers for polymerization to form the B blocksinclude: ethylene, propylene, butene-l, pentene-l, hexencl, heptene-l,octene-l, etc.

The criterion of glass transition temperature, or T,, has beenrecognized and used for many years to characterize polymers. Thistemperature, at which large segments of the main polymer chain becomemobile, can be determined by thermodynamic measurements, such asdifferential thermal analysis, heat capacity, and dilatometry.Ditferential thermal analysis (DTA) is preferred because it is rapid,reliable, reproducible, requires only a small sample, and permitsdetermining the crystalline melting point at the same time. Reported ormeasured glass transition temperatures for homopolymers prepared frommonomers preferred for use in the block polymers of this invention arelisted in Table III. A copolymer exhibits a glass transition temperaturecharacteristic of the monomers from which it is polymerized. A blockpolymer usually exhibits a separate glass transition temperature foreach block therein unless the T s of the individual blocks are so closetogether that they cannot be readily differentiated by the technique.

A preferred poly alpha-olefin block polymer has 3 connected blocks withthe terminal positions occupied by A blocks and the center positionoccupied by a B block. A designates a thermoplastic block which is ahomopolymer of propylene polymerized such that each is capable ofcrystallization. Each A block has a glass transition temperature aboveabout -60 C. and a crystalline melting point above 100 C. B designates athermoplastic block which is a copolymer of ethylene and propylenepolymerized such that it is substantially amorphous and has a glasstransition temperature below about 0 C. The propylene A blocksconstitute between about 25 to mole percent of the total block polymerand the ethylene-propylene copolymer B block constitutes correspondinglybetween about 75 to 25 mole percent of the total block polymer. Theoverall block polymer itself exhibits at least one glass transitiontemperature below about 0 C., at least one above about -60 C., acrystalline melting point above about 50 C. and is characterized bydispersibility in such hydrocarbon solvents as heptane, hexane, toluene,xylene, and cyclohexane, or blends thereof to provide a stable,pourable, homogeneous dispersion.

PREPARATION OF POLYMER Preparation of the poly alpha-olefin blockpolymers used in the invention typically employs a Ziegler-Natta typecatalyst, prepared either separately or in situ. Suitable catalystsinclude vanadium oxytrichloride, with aluminum alkyls or halo alkyls ascocatalysts. In general, the preferred catalyst system consists of atransition metal in a high oxidation state and a reducing agent which istypically an aluminum alkyl. The catalyst is most active and gives thefastest reaction rate and highest yield per gram of catalyst when thecatalyst and co-catalyst are mixed in situ in the presence of themonomer.

In general, the appropriate monomer is first introduced into a pressurereaction vessel in the presence of the selected catalyst together with asolvent such as hexane, chlorobenzene, heptane, or toluene. The first Ablock is polymerized to the desired molecular weight as measured byinherent viscosity; the chain length attained, being a direct functionof the quantity of monomer introduced into the reaction vessel. Themonomer or monomers from which the B block is polymerized is thenintroduced directly into the reaction vessel, and polymerized onto theend of the A block; the chain length attained again being a directfunction of the quantity of monomer introduced. At completion of thepolymerization of the B block, the monomer for the next A block isintroduced and polymerized on the free end of the B block. Thisprocedure is repeated until the desired number of blocks is attained. Itis possible to prevent copolymerization of one block with another fromoccurring by removing unreacted monomer before proceeding withpolymerization of the next block. Alternatively, monomers for any blockcan be introduced before the previous block has completedpolymerization, thereby reducing sharpness of the intersection betweenthe two blocks.

The progress of the polymerization can readily be determined bymeasuring the inherent viscosity of samples withdrawn at intervals fromthe polymerization reaction. Viscosity of the samples will show a steadyincrease, corresponding to progress of the polymerization. To obtain thecombination of polymer properties needed for preparing adhesives, inks,primers, etc., inherent viscosity (as determined in tetralin at 135 C.)after polymerization of the first A block should be at least about 0.5dl./ gm. at 0.1% weight per volume. After the polymerization of thefirst B block, inherent viscosity should be at least 1, and the inherentviscosity of the final polymer, regardless of the number of blocks itcontains, should be at least about 1.2. The maximum inherent viscosityobtained is never more than about 7. Typical inherent viscosities areshown in Table IV.

Increasing the chain length of a B.block relative to the A blocksincreases ultimate elongation of the polymer. Tacticity of any givenblock is inversely related to reaction temperature during its formation.Since the percentage of a polymer capable of crystallizing is a functionof the polymerization temperature it is possible to advantageouslyprogram polymerization temperatures to provide crystalline and amorphoussequences in a block.

Thus, this principle permits formation of poly alphaolefin blockpolymers from a single monomer wherein the block polymer has alternatingamorphous blocks and blocks capable of crystallization. An A block atleast capable of crystallization is first polymerized near the maximumtemperature utilizable, the temperature raised at least 25 C., asubstantially amorphous B block polymerized, and then the reactor isreturned to substantially the original temperature and another A blockpolymerized. This sequence can be repeated to obtain the desired numberof blocks.

Polymers prepared in accordance with this invention are readilydispersible at room temperature in hydrocarbon solvents such as hexane,heptane, etc., by use of a laboratory roller mill or mixer to providestable, pourable, homogeneous dispersions.

PREPARATION OF ADHESIVES, INKS, AND PRIMERS A particular advantage ofthese high tensile strength block polymers is their compatibility withtackifying resins, permitting formulation of a wide variety ofcompositions. For example, a preferred pressure-sensitive adhesive canbe formulated from a block polymer relatively low in tensile strength(e.g., 200 p.s.i. to 1000 p.s.i.), and a suitable tackifying resin suchas a polyterpene, sta

bilized ester resin, or hydrogenated rosin. A preferred general purposesolvent-dispersed adhesive can be formu lated from a block polymer ofintermediate tensile strength (e.g., 500 p.s.i. to 1500 p.s.i.). Apreferred heat-bonding adhesive can be formulated from a block polymerof intermediate to high tensile strength (e.g., 1000 p.s.i. to 5000p.s.i.). The choice of tackifying resin is determined by degree of tackneeded, softening point desired, color, and compatibility with suchother components as extender oils, stabilizers, plasticizers, pigments,etc. A compatible solution of the polymer and tackifier in appropriatesolvent does not irreversibly separate into phases or settle whenallowed to stand for extended periods of time. The amount of tackifyingresin needed varies with the particular polymer and end use. It canrange from about 5 parts by weight per 100 parts of polymer to about 300parts by weight of resin per 100 parts of polymer. In general, apreferred composition will contain the following parts by weight oftackifying resin per 100 parts of block polymer: pressure-sensitiveadhesive, about to 300; a general purpose solvent-dispersed orsolvent-activated adhesive, about 50 to 200; a heat-activated adhesive,about 5 to about 150; primer, about 25 to about 200.

Suitable tackifying resins include polyterpenes, stabilizedpolyterpenes, terpene-phenolics, hydrogenated rosin, esters ofhydrogenated rosin, esterified wood rosin, stabilized ester resin,styrene copolymers, hydrocarbon resins, and chlorinated hydrocarbonresins.

The following examples, in which all parts are by weight unlessotherwise noted, illustrate preparation of the polymers, adhesives,inks, and primers of this invention, without limiting the scope thereof:

DESCRIPTION OF PREFERRED EMBODIMENTS Example 1 This example illusratesthe general method by which the polymers are prepared, particularly a 3block polymer having low tensile strength, polypropylene end blocks andan ethylenezpropylene copolymer center block.

A 1500 ml. pressure vessel fitted with a mechanical stirrer wasevacuated, filled with dry pure nitrogen and re-evacuated. Whilestirring vigorously, 175 ml. of heptane, 1 gram of diethyl aluminumchloride in 20 ml. hep tane, 40 percent of the monomer for the first Ablock (0.08 mole of propylene), 0.5 gm. (0.00347 mole) of vanadiumoxytrichloride in 50 ml. of heptane, 200 ml. of dry heptane and theremainder of the monomer for the first block (0.12 mole propylene), wereintroduced in order.

Temperature of the reaction mixture was maintained at 1017 C. bycirculating water around the reaction vessel. The first A block waspolymerized for about 60 minutes, at the end of which time substantiallyall propylene had reacted, as was evidenced by no further pressure-dropin the vessel. The reaction mixture was then heated to 30 C. and 0.125mole each of ethylene and propylene introduced to form a B copolymerblock. After 60 minutes at 30-32 C., the reaction vessel was cooled toabout 18 C., monomer for the third block (0.2 mole of propylene)introduced and polymerized for about 150 minutes. Nitrogen was thenintroduced and the polymer suspension poured into an acidified methanolsolution. The golymer was washed several times with methanol and ried.

Dried polymer was formed into a flat self-supporting sheet by means of alaboratory press and physical properties were determined. Tensilestrength was 456 p.s.i., elongation was 1,030 percent, and glasstransition occurred at -54 C. and 20 C. as determined by differentialthermoanalysis. The final inherent viscosity of the polymer (asdetermined in tetralin at 135 C.) was 1.73. The polymer was 32% solublein diethyl ether maintained at its boiling point for 10 minutes, solublein n-heptane maintained at its boiling point for one hour, anddispersible in n-hexane at room temperature to provide A 37.8 literpressure reactor was charged with 12 kg. of heptane, 40 gms. of diethylaluminum chloride, and 20 gms. of vanadium oxytrichloride. Sixteen molesof propyl ene were introduced and the first block A polymerized until aninherent viscosity of 2.4 was reached. The reactor was evacuated andmoles each of ethylene and propylene introduced and polymerized until aninherent viscosity of 4.2 was reached. The reactor Was evacuated and 16moles of propylene introduced and polymerized until an inherentviscosity of 4.5 was reached. Physical properties of the resulting blockpolymer are illustrated in Table 1.

Examples 5-13 and physical properties of the resulting block polymersare illustrated in Table 1.

Example 14 This example illustrates preparation of a pressure-sensitiveadhesive. One hundred parts of block polymer prepared in accordance withExample 6 was dispersed in 650 parts of hexane and 125 parts ofpolyterpene resin having a melting point of about 115 C. and an acidnumber of about 1 was added. This dispersion was coated on primed 1 milpolyester film and dried at room temperature to form apressure-sensitive adhesive tape. The resulting dry coating weight was 9/4 grains per 24 square inches. Tack and adhesion of this tape werecompared to a tape formed by coating a commercially availablepressure-sensitive adhesive on the same backing, and dried in the samemanner. The pressure-sensitive adhesive tape of this example was alsocompared with commercially available transparent pressure-sensitivetapes, one having rubber-resin adhesive and the other having an acrylateadhesive. Samples of these four tapes were applied to a rigid untreatedpolypropylene sheet by means of a roll laminator at room temperature.The specimens were allowed to age at room temperature for 24 hours, andtested for peel strength. The polypropylene sheet was clamped in anInstron tensile machine and the tape peeled back on itself at an angleof 180 at a test speed of 12 inches per minute (ASTM D903). Thepressure-sensitive adhesive showed a peel strength of 9-10 lbs. per inchof width, while the other three pressure-sensitive adhesives and tapesgave a maximum of only 2.6 lbs. per inch.

Example 15 This example illustrates preparation of a general purposesolvent dispersed adhesive. One hundred parts of the polymer of Example6 was mixed with 800 parts of hexane, 100 parts of the polyterpene resintackifier used in Example 14 and dispersed by means of a mixer. Thisadhesive composition was tested by brushing two coats (with a minuteopen time between all coats) on various substrates and three coats on 1inch wide canvas strips. Thirty minutes after application of the lastcoat, the adhesive surfaces were placed in contact and the resultinglaminate rolled with a 2 lb. metal hand roller to complete the bond. Thecompleted bonds were allowed to dry at room temperature for one day andat 120 F. for two days. Each bond was then tested on a Scott tensiletester by peeling the canvas strip back on itself at an angle of 180 ata rate of 2 inches per minute. The results of each of these tests areshown in Table II below. One of the best commercially available priorart general purpose solvent dispersed nitrile-phenolic adhesives wastested in the same manner. These results are also tabulated in Table II.

Example 16 This example was prepared and tested in the same manner asExample 15 except that 150 parts of tackifying resin was used with partsof polymer. The results are indicated in Table II.

Example 17 This example was prepared and tested in the same manner asExample 15 except that parts of tackifying resin was used with 100 partsof polymer. The results are indicated in Table II.

Example 18 This example illustrates preparation of a decorative andprotective laminating film utilizing a heat-bonding adhesive. Onehundred parts of block polymer prepared in accordance with Example 6 wasdispersed in 800 parts of hexane and 100 parts of polyterpene resin ofExample 14 was added. This dispersion was then coated on 3 milpolypropylene film, which had previously been printed with a decorativepattern, and dried at a temperature of 150 F. for 20 minutes to form aheat-bondable laminating film.

This laminating film and a standard heat-activated vinyl veneerlaminating film, were adhered to a rigid polyethylene sheet by means ofa heat laminator at F. The bonds were tested for peel strength asdescribed in Example 15. With the adhesive of this example, thepolypropylene film backing broke at about 7 lbs./in. while the prior artadhesive failed to 0-0.25 lb./in.

Example 19 The process of Example 18 was repeated with the polymer ofExample 1 and 100 parts of hydrogenated rosin having a softening pointof about 74 C., a minimum acid number of 158, and a saponificationnumber of 167; to formulate a pressure-sensitive adhesive. This wascoated and dried on the same polypropylene film in Example 19. Theadhesive was very tacky to the touch.

This laminating film and a standard commercially available vinyllaminating film (acrylate adhesive) were each adhered to a rigidpolyethylene sheet by means of a roll laminator at room temperature. Thebonds were tested for peel strength as in Example 15. Peel adhesion was5.5 lbs/in. with the adhesive of this example, while the prior artadhesive gave only 0. 1-1.2 lbs./ in.

Example 20 This example illustrates preparation of pressure-sensitiveand heat-bondable transfer films for use as self-supporting adhesivetapes. The adhesives of Examples 19 and 18 were individually coated onrelease liners, dried for 20 minutes at 150 F., cooled, and wound intoroll form. Each of these films readily releases from the liner to give aself-supporting adhesive film for adhering two surfaces to each other bypressure or heat and pressure.

Polydodecene-l About 36.

Examples 21-22 These examples illustrate preparation of primers suitablefor use in adhering synthetic paint finishes to both high and low energysurfaces. The primer formulations of Table V were individually preparedby placing all of the components in gallon containers and mixing themfor about 24 hours on a laboratory roller mill. The primers were thenfurther dispersed for about minutes by means of a high speed laboratorypropeller mixer, smooth homogenous mixtures being obtained.

The primers were each brushed onto 4;" thick polypropylene test panelsand dried at 160 F. for minutes. A coating of automotive interior paintwas then sprayed over the primers and allowed to dry for 24 hours atroom temperature. Each panel was then subiected to the standardcross-hatch test by (1) making a series of parallel and perpendicularrazor blade cuts about A2" apart in the paint and primer, (2) applying astrip of Scotch Brand cellophane tape over the cuts, (3) rubbing thetape surface with a pencil eraser, and (4) quickly removing the tape atapproximately a 90 angle.

Adhesion of the paint to the primer and of the primer to thepolypropylene was excellent. The tape removed only very small amounts ofpaint or primer and then only from the cuts themselves. Primed andpainted test panels which had been immersed in 23 C. water for 100 hourswere tested in the above manner, the primer providing excellent adhesionof the paint to the polypropylene. Control test panels, some utilizingstandard automotive primer and others without any primer, were subjectedto the crosshatch test with almost all of the paint being removed by thetape in each case.

The primer formulations of this example were evaluated on metal testpanels in the manner previously described and were found to provideexcellent anchorage of the paint to the test panel. There was verylittle removal l Tackifier as utilized in Example 14. 1 50% solids byweight in xylene. 3 Reagent grade.

Example 23 This example illustrates preparation of an ink suitable forsilk-screening, stenciling, etc.

One hundred grams of the polymer of Example 6 was combined in a 3.78liter container with 200 gms. of polyterpene resin from Example 14, 400gms. of hexane, 400 gms. of toluene, and 137.5 gms. of predispersedcarbon black by weight in petroleum naphtha). The mixture was stirredwith a laboratory propeller mixer until a smooth homogenous dispersionwas obtained. The ink was coated on a polypropylene substrate, dried,and subjected to the cross-hatch test described in Examples 21-22.Essentially no ink was removed by the tape.

What we claim is:

1. In a solvent-dispersible composition comprising an elastomericpolymer dispersible in hydrocarbon solvents and an effective amount ofat least one tackifying resin selected from the group consisting ofterpene-phenolic, hydrogenated rosin, esters of hydrogenated rosins,esterified wood rosins, styrene copolymer, hydrocarbon resin, andchlorinated hydrocarbon resin, the improvement comprising:

utilizing as said polymer a substantially linear block polymer having aminimum tensile strength of about 200 lbs. per square inch, a minimumelongation of about 400%, an inherent viscosity of about 0.5 to about 7dl./gm. as determined at 0.1% weight per volume in tetralin at C., atleast one glass transition temperature below about 0 C., a crystallinemelting point above 50 C. as determined by differential thermalanalysis,

said block polymer consisting essentially of an odd number of connectedpoly alpha-olefin blocks and having the general configuration A-(BA)wherein n represents an integer from 1 to 4 inclusive, and the A blocksare at least capable of crystallization, have a glass transitiontemperature above about --60 C. as determined by dififerential thermalanalysis, a crystalline melting point above 100 C., and consistessentially of a polymer formed from propylene or butene-l or both, andthe B blocks are substantially amorphous, have a glass transitiontemperature below about 0 C., and consist essentially of a polymerformed from one or more alpha-olefin monomers each having the generalformula C H wherein n is an integer from 2 to 12, which monomer ormixture of monomers is capable of being polymerized so as to exhibit aglass transi tion temperature below about 0 C.,

whereby said solvent-dispersible composition has specific adhesion forpolyethylene and polypropylene and such other adherents as metals.

2. The composition of claim 1 wherein the block polymer has less thansix blocks.

3. The composition of claim 1 wherein the block copolymer has threeblocks.

4. A decorative and protective laminating sheet material comprising aself-supporting polymeric film coated on one side with the adhesive ofclaim 1.

5. A transfer film comprising a self-supporting free film of theadhesive of claim 1 releasably adhered on one side of a thin flexiblesheet backing whereby the adhesive film can be removed from the backingand used as a bonding film.

6. A printing ink comprising the composition of claim 1 and an effectiveamount of pigment.

7. A primer comprising the composition of claim 1 and an eifectiveamount of pigment.

8. The composition of claim 2 wherein each alpha-olefin monomer used toform 8 blocks are selected from the group consisting of ethylene,propylene, and butene-l.

9. The composition of claim 3 wherein the first A block is a polymer ofpropylene having an inherent viscosity greater than 0.5 as measured intetralin at C., a glass transition temperature above about 60 C., and acrystalline melting point above 100 C., and

the B block attached to one end of the first A block is a substantiallyamorphous copolymer of propylene and ethylene copolymerized such thatcombined blocks A and B have an inherent viscosity greater than about1.0, and the final total block copolymer has a glass transitiontemperature below 20 C. attributable to said copolymer block, and

the second A block attached to the free end of the B block, is a polymerof propylene polymerized such that the total block copolymer has aninherent viscosity of about 0.5 to about 7 dl./grn. as measured intetralin at 135 C.

10. The printing ink of claim 6 wherein the pigment is carbon black.

11. The primer of claim 7 wherein the pigment is iron oxide.

12. The composition of claim 9 wherein the tackifying resin is ahydrogenated rosin.

13 14 13. The composition of claim 9 wherein the tackify- 3,330,7917/1967 Mater et a1. 260-336 ing resin is a polyterpene. D 3,480,696 11/1969 Hassell et a1 260878 14. flhe composition of claim 9 wherein thetackrfy- FOREIGN PATENTS mg resin is a hydrocarbon resin.

15. A normally tacky and pressure-sensitive adhesive 5 915,622 1/1963Great i i tape comprising a thin flexible sheet backing coated on at957,060 5/ 1964 Great Bfltaln- 1 t rfacew'thth adhe' of la' 9.

eas one major su 1 e SW8 6 HOSEA E. TAYLOR, Primary Examiner ReferencesCited W. E. PARK-ER, Assistant Examiner UNITED STATES PATENTS 10 Us.CLX'R 3,239,478 3/1966 Harlan 260-27 3,325,430 6/1967 Grasley 260-25

